The present invention relates to an EL display panel and, more particularly, to a drive system of an EL display panel.
The present invention relates, more specifically, to a writing method for writing desired information into an EL display panel which shows memory characteristics.
An electroluminescent element of a three-layer construction is well known in the art, which comprises a semiconductor electroluminescent thin film made of, for example, a ZnS layer doped with Mn (ZnS:Mn) or a ZnSe layer doped with Mn (ZnSe:Mn) sandwiched between a pair of dielectric thin films made of Y.sub.2 O.sub.3, Si.sub.3 N.sub.4, TiO.sub.2, Al.sub.2 O.sub.3, or SiO.sub.2. The above-mentioned electroluminescent element exhibits electroluminescence of a high brightness upon receiving an A.C. voltage signal of several kilohertz. And, the above-mentioned electroluminescent element of a three-layer construction shows the long life operation.
By properly controlling the amount of Mn doped within the electroluminescent layer and the fabrication conditions, the above constructed electroluminescent element exhibits the hysteresis properties within light intensity versus applied voltage characteristics as disclosed by Y. KANATANI et al, U.S. Pat. No. 3,967,112, "PHOTO-IMAGE MEMORY PANEL AND ACTIVATING METHOD THEREOF" on June 29, 1976.
A typical drive method for the above-mentioned electroluminescent element of the three-layer construction was disclosed in the above-mentioned U.S. Pat. No. 3,967,112, wherein the photo-image is applied onto the electroluminescent element, and the thus written image is held by applying a sustaining alternating signal to the electroluminescent element.
Generally, the electroluminescence of the electroluminescent element can be controlled through the use of a voltage signal applied across the electroluminescent layer, or light or heat applied to the electroluminescent layer. When the electroluminescent element has hysteresis loop characteristics, the combined control of the sustaining voltage and the write-in signal comprising a write-in voltage signal or a write-in optical beam signal will considerably increase the application of the electroluminescent element in various fields.